Liquid fraction collecting apparatus



Sept. 14, 1965 E. PACKARD ETAL LIQUID FRACTION COLLECTING APPARATUS 8 Sheets-Sheet 1 Filed April 10 1962 NVENTORS LYLE E. bAcKARD STEVE M. Buu Eomuno FRANK 114%,MM, W-I6M A'r'ws,

Sept. 14, 1965 L. E. PACKARD ETAL LIQUID FRACTION COLLECTING APPARATUS Filed April 10, 1962 8 Sheets-Sheet 2 INVENTORS LYLE E. PACKARD STEVE M. Buu Eowmw FRANK by: W 7

Sept. 14, 1965 E. PACKARD ETAL 3,205,921

LIQUID FRACTION COLLECTING APPARATUS Filed April 10, 1962 8 Sheets-Sheet 3 INVENTORS L L E. PACKARD s'revs M. Buu

Evmmo FRANK ATTYS.

Sept. 14, 1965 E. PACKARD ETAL 3,205,921

LIQUID FRACTION COLLECTING APPARATUS Filed April 10, 1962 s Sheets-Sheet 4 mvamozzs LYLE E. PACKARD STEVE M. Buu Eonuma Fnmx 7 MAJ,

Sept. 14, 1965 L. E. PACKARD ET AL 3,205,921

LIQUID FRACTION COLLECTING APPARATUS Filed April 10, 1962 8 Sheets-Sheet 5 I I R 5Q m INVENTORS LYLE E. PACKARD STEVE M. Buu

"H Ermuuo FRANK Sept. 14, 1965 E. PACKARD ETAL 3,205,921

LIQUID FRACTION COLLECTING APPARATUS Filed April 10, 1962 8 etseet 6 INVENTORS LYLE E. PACKARD STEVE M. Buu EDMUND FaANk Sept. 14, 1965 L. E. PACKARD ETAL LIQUID FRACTION COLLECTING APPARATUS 8 Sheets-Sheet 8 Filed April 10, 1962 INVENTORS LYLE E. PACKARD STEVE M. Buu Enmmo FRANK b 11/4,, MAJ, flaw/MM Unite Smtes Patent LIQUID FRACTION COLLECTING APPARATUS Lyle E. Packard, Hinsdale, Steve M. Bun, Brookfield, and

Edmund Frank, Chicago, 11]., assignors to Packard Instrument Company, 1110., Lyons, Ill., a corporation of Illinois Filed Apr. 10, 1962, Ser. No. 186,524 12 Claims. (Cl. 141-94) The present invention relates in general to apparatus for collecting successive liquid fractions or samples of flowing streams. More particularly, the invention pertains to an improved liquid fraction collector especially suitable for use in collecting successive portions of effluent streams passed through one or more chromatographic columns, although the invention will find advantageous use in other specific applications.

It is a general aim of the present invention to provide an improved liquid fraction collector which is entirely automatic in operation and which is characterized by its ability to collect a relatively large number of samples, or liquid fractions, either from a single chromatographic column or simultaneously from a plurality of diflferent chromatographic columns.

A related object of the invention is to provide a liquid fraction collector which, despite its ability to collect a relatively large number of samples, is nevertheless characterized by its compact size, thereby permitting the installation of the apparatus under a Wider range of space conditions than heretofore possible.

It is a further object of the invention to provide a novel indexing mechanism for a fraction collector which permits sequential collection of samples from any given chromatographic column, yet wherein samples collected from different columns are collected in different corresponding sample racks, thus permitting independent removal of the samples collected from each column. In this connection, it is an object of the invention to provide an indexing mechanism for fraction collectors or the like which will automatically return to the starting or home position after a predetermined number of samples from any one or more different columns have been collected.

A coordinate object of the invention is to provide an indexing mechanism which will automatically return to the home position in the event that a light source for the photoelectric drop counting head should be extinguished for any reason, thus preventing excessive filling of a particular sample container and resultant overflow therefrom due to faulty operation of the counting or indexing mechanisms, and minimizing the loss of efiluent and the danger of contamination of the collecting apparatus.

An ancillary object of the invention is to provide a liquid fraction collector of the type employing removable stationary sample racks, thus permitting immersion of the sample containers in a cooling bath during collection periods.

In another of its aspects, it is an object of the invention to provide a fraction collecting apparatus wherein either a predetermined number of drops of efiluent may be counted into each sample container or wherein efl luent will be collected in each sample container for a predetermined time interval, yet where the same basic electrical components are used to effect indexing movement to the next sample container irrespective of whether a drop counting operation or a time measuring operation is performed. While not so limited in its application, the ability to collect liquid fractions in successive containers for predetermined time intervals is particularly advantageous when simultaneously collecting fractions from a plurality of different columns, each of which may be of difierent size or whose head conditions or liquid viscosity may vary. And of course, since the same basic electrical components are used in both time measuring and drop counting, a substantial saving in component cost is efiected.

An important advantage of the invention resides in the provision of selectively operable means for automatically collecting aliquot portions of a given eflluent in alternate sample containers and wherein such alternate aliquot portions are simultaneously collected in different sample racks for each different effluent being collected.

In another of its important aspects, it is a more specific object of the invention to provide an improved liquid fraction collector which is reliable in operation and which employs a minimum of switches of the type having relatively moving parts subject to wear, sticking or other faulty operations. To attain this objective, the indexing steps of the movable counting head are controlled by printed circuit conductive segments carried on the frame of the machine and on the cross beam which supports the counting head. This printed circuit arrangement permits interruption of the current supply for the light source in the photoelectric counting head when the latter is indexed to a position exceeding its limit positions, thus extinguishing the light and automatically -homing the counting head.

These and other objects and advantages of the invention will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a fraction collecting apparatus embodying the features of the present invention, here shown with a portion of the cover removed and in conjunction with four different chromatographic columns, the lower ends of the columns being depicted by broken lines;

FIG. 2 is a fragmentary plan view of the fraction collecting apparatus of FIG. 1 with the front frame of the apparatus presented at the top of FIG. 2 and here shown with the cover, including the structure for supporting chromatographic columns and the rear control panel, removed, and with the sample collecting tubes visible;

FIG. 3 is a rear view of the apparatus shown in FIG. 2 illustrating particularly the timing mechanism and portions of the driving mechanism for actuating the rectilinear indexing mechanism;

FIG. 4 is an elevational view taken substantially along the line 44 of FIG. 2 and illustrating particularly the details of the timing mechanism;

FIG. 5 is a sectional view taken substantially along the line 5-5 of FIG. 2 and illustrating particularly the details of the Y axis stepping motor driving connection;

FIG. 6 is a sectional view taken substantially along the line 66 of FIG. 2 and illustrating particularly the arrangement for stepping the counting head along the Y axis;

FIG. 7 is a sectional view taken substantially along the line 7-7 of FIG. 6;

FIG. 8 is a sectional view taken substantially along the line 88 of FIG. 2 and illustrating the details of the carriage used to effect incremental stepping of the counting head along the X axis;

FIG. 9 is a fragmentary elevational view of the printed circuit arrangement employed to effect incremental stepping along the X axis;

FIGS. 10 through 12 are fragmentary elevations of the printed circuit arrangements formed on the cross beam which supports the counting head;

FIG. 13 is a plan view, partly in section, of an exemplary drop counting head;

FIGS. 14a and 14b are block-and-line diagrams which, when placed side by side and considered conjointly, il

lustrate the control system for effecting rectilinear indexing of the counting head;

FIG. is a schematic circuit diagram of an exemplary monostable device employed in the control system illustrated in FIGS. 14a and 14b; and

FIG. 16 is a schematic circuit diagram of an exemplary one of the bi-stable devices used to drive the stepping motors.

While the invention is susceptible of various modifications and alternative constructions, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

streams such, for example, as chromatographic columns.

However, in order to make clear one environment, the invention is here illustrated and described in connection 'with a fraction collector of the type suitable for collecting a plurality of samples in sequential order from a single chromatographic column or, alternatively, for simultaneously collecting a plurality of sequential samples from each of two or more chromatographic columns.

To this end, the liquid fraction collecting apparatus 25 shown in FIG. 1, includes a base 26 designed to receive and support four independent sample storage racks or trays 28a-28d, each mounted on a different quadrant of the rectangular base. transversely across the rear of the fraction collector 2S and contains the power supply and the electrical and mechanical control components associated with the apparatus 25. The housing 29 also serves to support a forwardly presented control panel 38 and storage cornpartment 31, the latter being particularly suited for retaining auxiliary and spare parts. In order to maintain the trays or racks 28a-28d in a substantially enclosed compartment, thus minimizing the danger of dust or other contaminates entering the independent sample containers (for example, test tubes or the like as shown in FIG. 2), while at the same time providing for visual inspection of the samples collected, a transparent cover 32 is supported adjacent its rear edge on the housing 29 and adjacent its forward edge on the front frame 34 of the apparatus 25. The cover 32 may, merely by way of example, be made of glass or of a flexible transparent sheet of plastic material (e.g., polyethylene).

To facilitate ready insertion and withdrawal of one or more of the storage racks Zita-28d, provision is made for hinging the cover 32 so that it may be moved to an open position. In the exemplary apparatus shown in FIG. 1, this may simply be accomplished by securing one end of each of a pair of horizontally spaced rods 35 to the respective upper corners of the frame 34, the opposite ends of the rods 35 being secured to the housing 29.

Thus, if a flexible cover 32 is employed, it rests upon the rods 35 and the overhanging portions form side walls 36 which depend downwardly from the rods. Of course, if the cover 32 is made of a rigid material such as glass, it would be necessary to provide a suitable hinge (not shown) at the junctions of the side walls 36 and the top of the cover 32. In either instance, when the operator desires to change one or more of the sample racks 28a- 28d, it is only necessary to pivot one or both side Walls A box-like housing 29 extends 36 upwardly about the corresponding rods 35, thus providing access to the sample collecting compartment through the sides of the apparatus 25.

In order to support the glassware generally associated with chromatographic columns, a spider, generally indicated at 38, having a cylindrical hub 39 is carried by the frame of the fraction collector 25. In the illustrative apparatus, the spider 38 is rigidly mounted on three vertical posts 40, two of which are carried at opposite ends of the housing 29 while the third is secured to the base 26 at approximately the midpoint of the front wall or frame 34. The arrangement is such that the cylindrical hub 39 is located above the cover 32 and slightly offset from the midpoint thereof. To facilitate support of one or more chromatographic columns (the lower ends of four such columns Mia-41d here being shown diagrammatically by broken lines), the hub 39 is intended to receive the lower end of an elongate post 47 which may be rigidly locked therein by any suitable means (not shown). Laterally extending arms 44 are releasably clamped to the post 47, each arm being provided with a clamp 45 adjacent its extremity for receiving and holding a respective one of the chromatographic columns 41a- 4ld at points disposed above and in substantial alinement with the midpoints of the respective storage racks 28a28d.

For permitting communication between the chromatographic columns and the test tubes or sample containers which are supported in the storage racks, the cover 32 is provided with a plurality of openings (seven such openings 46a46g being shown in FIG. 1), each having a rubber bushing 48 adapted to snugly receive the lower end of a corresponding column. As the ensuing description proceeds, those skilled in the art will appreciate that it is desirable for each column to be located over the approximate midpoint of the storage rack or racks collecting samples from that column. Thus, when the apparatus 25 is used as shown in FIG. 1 to collect samples from four diiferent columns 4111-4111 in corresponding ones of four different racks 28a-28d, the lower ends of the columns respectively extend through the openings 46a-46d which are alined with the approximaate midpoints of the corresponding racks 28a-28d. If, however, the apparatus 25 were being used to collect samples from only two different chromatographic columns in the four racks, each column would discharge etfluent successively into two different trays. For example, column 41a might discharge eflluent into racks 28a and 28b while column 41c might discharge eflluent into racks 28c and 28d. In that case, the arms 44 supporting columns 41a and 410 would be shifted laterally so that the lower ends of the two columns become alined with an extend through the openings 46a, 46 respectively the latter being located at the approximate midpoints of the pairs of trays 28a, 28b and 28c, 28d. Alternatively, if the apparatus 25 is being used to collect samples from only a single column (e.g., column 41a) in all four racks 2801-2861, the arm 44 supporting that column might be adjusted so that the lower end of the column is alined with the opening 46g, the latter being located centrally of all four racks.

Of course, while the exemplary apparatus has been described in connection with a particular support arrangement for the chromatographic columns or column, it will be understood that such an arrangement is not critical to the present invention and numerous other support arrangements could be employed. Merely by way of example, it would be entirely within the scope of the invention to support the individual columns from one or more of the vertical posts 40 in such a manner that the columns are substantially alined with respective openings in the cover 32.

As best illustrated in FIG. 2, it will be observed that each of the storage racks 28a-28d provide means for holding one-hundred sample containers or test tubes 48 in a X 10 array, the tubes bein supported on equally spaced centers, e.g., centers spaced one inch apart. Thus, all four racks serve to support a total of four hundred test tubes in a relatively compact area, thereby minimizing unused space.

In accordance with one of the important aspects of the present invention, there is provided a novel fraction COI- lecting apparatus having sample storage racks disposed in side-by-side relation and, in the exemplary form of the invention, disposed in each different quadrant of the apparatus, together with a rectilinear indexing mechanism for effecting incremental movement of a drop counting head along both X and Y coordinates of the apparatus to index positions alined over successive sample collecting test tubes 48 in a given rack, and for indexing the drop counting head over the different racks in sequential order. In the exemplary form of the invention, this is accomplished by indexing the counting head through positions alined with successive test tubes in a first and outer row of a given quadrant, shifting the counting head to a second row in that quadrant adjacent to the outer row, and then indexing the counting head in the reverse direction in the second row. This rectilinear sequence of indexing movements is repeated row by row until each test tube in that quadrant has received a quantum of the sample or effiuent being collected. The counting head may then be indexed in a similar manner through sequential ones of the four quadrants in such a manner that upon completion of filling the last test tube in the last quadrant, the counting head will return to its initial starting or home position.

Referring now to FIG. 2, it will be observed that a drop counting head, generally indicated at 49, is initially disposed over one of the test tubes 48 carried in a corner of the rack 28a, the particular tube 4311 being located in an outer row of the entire rectilinear array of tubes and adjacent to a storage rack disposed in another quadrant, here shown as adjacent to the rack 28d. For purposes of simplifying the ensuing discussion, the tube 4811 will hereinafter be referred to as that tube occupying the home position of the fraction collecting apparatus 25.

In order to facilitate an understanding of the novel indexing mechanism of the present invention, a brief description of the sequence of indexing steps will be described below, it being assumed for the purpose of this description that the fraction collecting apparatus 25 is being used to collect samples sequentially in all four storage racks from a single source.

Thus, in the exemplary apparatus the drop counting head 49 is first indexed along an X coordinate (i.e., to the left as viewed in FIG. 2) so as to be successively registered with each tube in that row. When a sample has been discharged into the last tube in that row (i.e.,

tube 48a), the head 49 is then indexed one step along a Y coordinate (upwardly as viewed in FIG. 2) to a position over the adjacent tube 481). The head 49 is then again indexed along an X coordinate (this time to the right over the second row as viewed in FIG. 2) until each tube in the second row has received a sample. The head 49 then indexes one step along a Y coordinate to register with the first tube in the third row. This rectilinear indexing operation is cotntinued to successively register the head 49 with each test tube 48 in the rack 23a, terminating with tube 480 in the upper right hand corner of the rack (as viewed in FIG. 2). The head 49 is then ready for a single step indexing movement along a Y coordinate to a position overlying the corner tube 43d carried in the rack 28b, and the indexing operation previously described is then repeated to discharge samples into all the tubes 48 carried by the rack 28b, terminating with the tube 48e in the upper right hand corner of that rack. Next, the counting head 49 is indexed to the initial corner tube 43 in rack 28c and all the tubes 48 in that rack receive a sample. Finally, the counting head 49 is indexed to the corner tube 48g in the rack 28d, and each tube 48 in that rack receives a sample, the last tube to be filled being tube 481' adjacent to the first tube 48h occupying the home position in rack 28a. The head is then returned to its initial or home position over tube 4811 in readiness for another indexing cycle.

To permit rectilinear indexing of the drop counting head 49 along a given X coordinate, the head is supported by a cross beam 50 which is slidably mounted adjacent its forward end on a track 51 integral with the front frame 34 (FIGS. 2 and 6) and rigidly mounted adjacent its rearmost end on a carriage 52, the latter being supported by and translatable along a shaft 53 journalled for rotation in oppositely disposed side plates 54, 55 integral with the frame and contained within the rear housing 29. Referring to FIGS. 2 and 6, it will be observed that the forward end of the beam 50 has rigidly secured thereto an idler block 56 made of a suitable bearing material such as nylon. The block 56 is provided with a transverse slot 53 adapted to receive a rearwardly projecting flange integral with the front frame 34 and defining the track 51.

For the purpose of shifting or translating the carriage 52 (and therefore both the beam 50 and the counting head 49 supported thereby) in incremental steps along an X coordinate, the carriage is coupled to a reversible X stepping motor SMx through a suitable drive cable 59 (FIGS. 2 and 4). In the exemplary apparatus, the opposite ends 69 and 61 of the cable 59 are connected to opposite sides of the carriage 52. The cable is trained about a drive pulley 62 rigidly mounted on the output shaft 64 of the stepping motor SMx, about a pair of idler pulleys 65, 66 journalled for rotation on a bracket 68 integral with the side plate 55, and about an idler pulley 69 journaled for rotation in the mounting bracket 70 carried by the side plate 54. To tension the cable so as to prevent slippage thereof relative to the drive pulley 62, the bracket 70 is resiliently mounted on the plate 54 by means of a compression spring 71, the latter being concentrically disposed about an adjusting screw 72 and interposed between the plate and the head of the screw. Hence, by suitable adjustment of the screw 72, the cable 59 may be properly tensioned to prevent cable slippage.

When the reversible X stepping motor SMx is energized to rotate the output shaft 64 in a counterclockwise direction (as viewed in FIG. 2) through a fixed angular increment, the carriage 52 will shift a corresponding fixed incremental distance to the left along the shaft 53. Consequently, the counting head 49 is also shifted to the left a fixed incremental distance. Conversely, if the output shaft 64 is driven in a clockwise direction through a fixed angular increment, the carriage 52 will shift a corresponding fixed incremental distance to the right along the shaft 53. In this latter instance, the counting head 49 is also shifted to the right along an X coordinate a fixed incremental distance.

In carrying out the present invention, provision is made for permitting sliding movement of the counting head 49 relative to the cross beam 50. To this end, and as best illustrated in FIG. 7, the cross beam 50 includes a pair of laterally spaced beams 74, 75 made of an insulating material such as nylon. The beams '74, 75 are held in spaced apart relation adjacent their rearmost ends by a forwardly projecting boss 76 (FIGS. 2 and 6) formed integrally with the carriage 52, While the idler block 56 serves to hold the beams 74, 75 in spaced apart relation adjacent their forward ends. In the exemplary form of the invention, the beams 74, 75 are housed within an elongate cover 78 having a substantially inverted U-shaped cross section. The cover 78 and beams 74, 75 are rigidly secured to the boss 76 by means of threaded fasteners 79 extending laterally therethrough (FIG. 6), While the beam and cover assembly is rigidly secured to the idler block 56 by means of a threaded fastener 80 (FIGS. 6 and 7).

The foregoing construction of the cross beam 50 is such that the spaced apart beams 74, 75 define a track for slidably supporting an upwardly extending body 81 integral with the counting head 49. As best illustrated in FIG. 7, the opposite sides of the body 8 1 are'recessed to define two pairs of vertically spaced shoulders 82, 83 and 84, 85 which slidably embrace the upper and lower edges of the beams 74, 75 respectively. Thus, the body 81 of the counting head .9 is securely confined between the beams 74, 75 while at the same time being free for slidable movement relative thereto between the boss 76 and the idler block 56.

For the purpose of translating or shifting the counting head 49 in incremental steps along a Y coordinate, a drive cable 86 has its opposite ends rigidly secured to the forwardly and re-arwardly presented edges of the body 81. The drive cable 86 is trained about a vertically oriented, arcuate slot $3 formed in the idler block 56 and over a drive pulley 89 which is slidably mounted on the shaft 53 for rotation therewith. The drive pulley 89 is retained on the shaft 53 by means of a radially disposed set screw 99 having its inwardly presented tip 91 slidably received within an elongate keyway slot 9-2 formed in the shaft 53. In order to insure that the carriage 52 and the drive pulley 89 slide along the shaft 53 as a unit, the latter is received within a pair of interconnected, laterally spaced body portions 52a, 52b of the former. Thus, as the carriage 52 is translated along the shaft 53 by energization of the stepping motor SMx, the drive pulley 89 is also translated therealong.

To effect incremental angular rotation of the drive shaft 53, the shaft is coupled to a reversible Y stepping motor SMy through a sprocket chain 94 (FIG. 3), the latter being trained over a pair of sprockets 95, 96 respectively mounted on the ends of the shaft 53 and the output shaft 98 of the Y stepping motor SMy.

Referring to FIG. 6, it will be appreciated that when the reversible Y stepping motor SMy is energized so as to rotate the shaft 53 in a counterclockwise direction through a fixed angular increment, the drive pulley 89 is also rotated through a corresponding fixed angular increment. Consequently, the body 81 of the counting head 4-9 will slide along the track defined by the spaced beams 74, 75 (i.e., along a Y coordinate) a corresponding fixed incremental distance (to the right as viewed in FIG. 6). Conversely, if the shaft 53 is driven in a clockwise direction through a fixed angular increment by the stepping motor SMy, the counting head will shift along the Y coordinate a corresponding fixed incremental distance to the left.

When the fraction collecting apparatus 25 (FIG. 1) is being used to collect a relatively large number of samples from a single source such, for example, as a single chromatographic column, the eflluent discharges from the column drop-by-drop and is conducted to the drop counting head 49 through a flexible catheter tube 99a (FIG. 7) having one end (not shown) coupled to the lower end of the chromatographic column which projects through the opening 46g located centrally in the cover 32 (FIG. 1). The opposite end of the catheter tube 99 is coupled directly to a nipple 10911 which is mounted in a bore 101 extending vertically through the counting head 49. A light source 1112 and a photocell 1114 (FIG. '13) are carried by the counting head 49 in a transverse bore 105, the latter intersecting the vertical bore 101. As shown in the illustrative form of the invention, the light source 1112 and photocell 104 are disposed on opposite sides of the vertical bore 1111 in such a manner that each drop of efll uent passing through the bore intercepts the light beam projecting thereacross, thus momentarily darkening the cell and producing an output signal therefrom.

As will be described in connection with the control circuits shown diagrammatically in FIGS. 14a and 14b, the output signals from the photocell 104 are counted and when a predetermined number of signals have been counted, a control signal is generated for energizing one of the stepping motors SMx or SM to effect an indexing step for the counting head. If, therefore, the fraction collecting apparatus 25 is set to collect a large number of samples from a single source, the counting head will be indexed one step each time that the predetermined number of drops from that source have been counted. The counting head 49 will move from test tube to test tube and from quadrant to quadrant in the manner previously described, until all of the test tubes have been filled.

Let it now be assumed that the operator desires to collect samples in each of the four racks 28:1-28d from four different corresponding chromatographic columns 4151-4162 (FIG. 1). To accomplish this, provision is made for supporting the lower ends of the four respective catheter tubes 99(1-99d in positions simultaneously overlying corresponding test tubes in the four quadrant racks 28a- Zfial, as best illustrated in FIGS. 2 and 7. As here shown a first laterally projecting extension arm 1% having a pair of wire members 166a, 1665, is securely attached directly to the counting head 49. To this end, the inboard end of each wire member includes a downwardly bent tip 1% adapted to be received in a corresponding bore 1119 formed in the counting head. The outboard end of the arm 1% serves to support a nipple 100d, the latter being coupled directly to the catheter tube 99d. The arm 1196 is dimensioned such that when the nipple 1110a on the counting head 49 overlies the lower right-hand corner test tube 48h in the rack 28a (as viewed in FIG. 2), the nipple 196d overlies the corresponding lower righthand corner test tube in rack 28d.

Two additional extension arms 119, 111 each having a pair of wire members Hilda-1111b, 1111141 111) are provided for supporting nipples 101311, 160:: on their outboard extremities overlying corresponding test tubes in racks 28c and 28d, respectively. The members Milo-1111b 111a-111b are each provide-d at their inboard ends with upwardly extending portions 112 adapted to be snugly received within corresponding bores 114 formed in a carrier v115, the latter being slidably mounted on the cross beam 50. Referring to FIG. 7, it will be noted that the carrier 115 is generally C-shaped in cross section, the laterally projecting arms thereof each being slotted (as shown at 116, 11 8) to ride along the upper and lower edges of a track v119 which is rigidly secured to the cover 78 on the cross beam 51). In the exemplary apparatus, the carriage 115 is mechanically coupled to the counting head 49 by means of a tie bar 120, the opposite ends of which are provided with downwardly turned portions 131 adapted to be received within bores 112 formed in the counting head 49 and carrier 115.

It will be apparent from FIG. 2 that the arms 1%, and 111 and the tie bar 121) are dimensioned such that the nipples limo-Mild will all overlie corresponding test tubes in the four respective racks Zita-28d (e.g., the lower right-hand corner test tube in each rack). Since the arms are all mechanically connected together, indexing of the counting head 49 and its discharge nipple 1110a will cause simultaneous indexing of the arms 1116, 1111 and 111 and their associated discharge nipples ltlilb-ltllld. Thus, to fill sample tubes 48 in all four racks 28a28d simultaneously, the operator need only attach the extension arms and carrier in the manner described above, couple the catheter tubes 99a-99d to both the corresponding columns Mel-41d and nipples Nita-100d, and then initiate an indexing cycle of operation.

If the operator desires to collect samples from only two columns, it would only be necessary to attach one extension arm, preferably the arm 106. In this instance, the counting head 49 would be successively indexed over all the tubes 48 in rack 28a while the discharge nipple 101111 on arm 106 would be successively indexed over all the tubes 48 in rack 28d. When the counting head 49 indexes to the rack 28b, the nipple 106d simultaneously indexes to the rack 28c. Thus, as here shown, the apparatus makes possible collection of approximately four hundred fractions from a single column, collection of approximately two hundred fractions from each of two columns or the collection of approximately one hundred fractions from each of three or four columns. When the tie bar 120, carrier 115 and arms 106, 110 and 111 are not being used, these components may be stored in the storage compartment 31 (FIG. 1).

One problem encountered when collecting samples from two or more columns resides in the provision of suitable means for measuring the desired quantity of effluent from the plurality of different columns. Generally, the efiiuent from such columns will have different viscosities or the head conditions in the columns will vary. Often, the columns will have different sizes. As a result of these varying conditions, the drop rate or drop size for the columns will vary. Consequently, it is not practical to index on the basis of a predetermined number of drops discharged from any one column, since the drops will vary from column to column. It has in such instances, been found more practical to discharge efiluent for a predetermined time interval.

In accordance with another important aspect of the present invention, provision is made for generating output pulses or signals as a function of elapsed time rather than as a result of drop counting. Such signals are then conducted to the same counting and control circuit (to be described in connection with FIGS. 14:: and 14b) employed with the drop counting system previously described. To provide such timed output signals in lieu of the drop counting signals emanating from the photocell 104, a selectively operable timing mechanism, generally indicated at 124, is mounted in the rear housing 29 (FIGS. 3 and 4). The exemplary timing mechanism 124 includes a constant speed motor 125 having an output shaft 126 (which, for example, may be driven at a speed of 50 r.p.m.). The shaft 125 supports an elongate chopper bar 128 positioned to periodically interrupt a light beam directed from a light source 129 toward a photocell 130, the light source and photocell being mounted on a U-shaped bracket 131 integral With the frame of the machine. The arrangement is such that the beam is interrupted twice during each revolution of the shaft 126 (Le, by each end of the chopper bar 128). Each time one end of the chopper bar 128 interrupts the light beam an output pulse from the photocell 130 is generated which is conducted to a pulse counter. With the exemplary arrangement, one hundred pulses per minute will be generated. Thus, if the counter is set, for example, to count one thousand pulses, the counting head 49 will be indexed every ten minutes and, during that ten minute interval, test tubes in different racks will simultaneously receive emuent from the associated chromatographic columns.

For the purpose of insuring precise indexing of the counting head 49, while at the same time achieving other control functions which will be explained in greater detail in connection with the novel control system shown diagrammatically in FIGS. 14a and 14b, a plurality of conductive segments are formed on an insulating board 134 rigidly mounted on the frame of the machine (FIG. 3), and on the spaced insulating beam arms 74, 75 in the cross beam 59 (FIGS. 12). Referring first to FIG. 3, provision is made for containing a suitable power supply pack, generally indicated at 135, within the housing 29, the pack 135 being electrically connected by suitable conductors (not shown) to diverse selected terminals of a plurality of conductive segments S1-S17 (FIG. 9) formed on the board 134. The conductive segments are wiped (during translation of the counting head 49 along an X coordinate) by respective ones of a plurality of brushes or wipers W1-W17, the latter being mounted on a brush holder 136 having upper and lower guides 138, 139 slidably engaging the upper and lower edges of the board 134 (FIG. 8). The brush holder 136 is, in turn, rigidly connected to the carriage 52 by means of a threaded fastener 140 (FIGS. 2 and 8). Thus, as the carriage 52 is translated along the shaft 53, the brush holder 136 slides along the insulating board 134 with the different wipers W1- 10 W17 in electrical contact with corresponding ones of the segments S1517.

Referring next to FIG. 7, it will be observed that seven wipers W13-W24 are mounted on and carried by the body 81 of thecounting head 49. The wipers W18-W24 are respectively positioned to make electrical contact with corresponding conductive segments SIS-S24 formed on different surfaces of the insulating beams 74, (FIGS. 1

10-12). With particular reference to FIGS. 7 and 12, it will be noted that the inboard surface of the beam 75 has formed thereon four conductive segments $18521 which are respectively wiped by wipers W18W21 during indexing along a Y coordinate. In similar manner the inboard surface of beam 74 (FIG. 10) has formed thereon two sets of conductive segments S22, S22 and S22a, 522a positioned to be shorted by a shorting brush or wiper 22 at particular points during indexing movement along a Y coordinate. Finally, the outboard surface of beam 74 (FIG. 11) has formed thereon a pair of conductive segments S23, S24 which are respectively wiped by wipers W23, W24 during translation of the counting head 49 relative to the beams. The wipers W23, W24 are supported on a bracket 141 which is rigidly secured to the body 31 by means of a threaded fastener 142.

In the exemplary apparatus, the wipers \Vl-W3 and W6-W12 are electrically coupled to the terminals of different ones of the conductive segments formed on the faces of the beams 74, 75 by means of a plurality of conductors, generally indicated at 144 in FIG. 6. Merely by way of example, the wipers W1 and W6 (positioned to wipe segments S1 and S6 which are respectively coupled to the negative and positive terminals of the power supply are connected to the segments S18, S19 respectively on the beam 75. The wiper W18 is coupled to one terminal of the light source 102 while the wiper W19 is coupled through the normally closed microswitch M81 to the other terminal of the light source 102. Thus, as the counting head 49 is indexed, an energizing circuit is completed for the light source.

In like manner, a circuit is completed for the photocell 104 through the segments S7, S8, Wipers W7, W8, segments S20, S21, and wipers W20, W21, the latter being connected directly to the terminals of the photocell 104. In order to complete a circuit suitable for providing stop signals for the Y stepping motor SMy, the segments S2, S3 are respectively coupled through wipers W2, W3 to segments S23, S24, the latter segments being wiped by interconnected Wipers W23, W24.

For the purpose of providing a control signal indicating that the counting head 49 has homed along a given Y coordinate, the segments S9, S10 are respectively coupled to the segments S22, S22 through wipers W9, V10. The segments S22, S22 are positioned to be electrically connected by Wiper W22 only when the counting head 49 occupies a position along a Y coordinate overlying a tube in the first row (i.e., that row of tubes shown in FIG. 2 containing tube 48h and lying in the X coordinate).

Finally, and as part of the energizing circuit for indicating that the counting head has completed an indexing cycle for the quadrant rack 28b and is ready to be indexed to the quadrant rack 280, the segments S11 and S12 are coupled directly to segments 822a and 822a through wipers W11 and W12, the latter segments positioned to be connected by the wiper W22 only when the counting head overlies that row of test tubes 48 (FIG. 2) along the X coordinate closest to the front frame 34.

In accordance with yet another aspect of the present invention, provision is made for energizing both stepping motors SMx, SMy whenever a malfunction occurs so that the counting head 49 will be automatically returned to its home position. As a typical example of one type of malfunction that might occur, let it be assumed that during a drop counting operation the light source 102 burns out. When this occurs, the column will conr tinue to discharge effluent drop-by-drop into the test tube 4S beneath the counting head but, since the light 102 is out, drops will not be counted and, hence, the head will not be indexed. As a result, the tube 48 will overflow. T o prevent this undesirable situation, and as will be described in greater detail in connection' with the description of FIGS. 14a and 14b, provision is made for generating an output signal whenever the light source 1&2 is extinguished (i.e., when the circuit through segment S1, wiper W1, segment S18, wiper W18, light 102 microswitch M81, wiper W19, segment S19, wiper W6 and segment S6 is not completed). Thus, should the light source 102 burn out or become extinguished for any other reason, a control signal is generated for energizing both stepping motors and returning the counting head 49 to its home position.

In carrying out this aspect of the invention, provision is made for automatically extinguishing the light source 102, and thus homing the counting head 49, whenever the counting head is indexed to a position exceeding its limit positions along the X and Y coordinates. Referring to FIG. 9, it will be noted that the conductive segment S1 is provided with an interrupted portion 145 adjacent one end thereof (the right end as viewed in FIG. 9) and terminates short of the other segments adjacent its opposite end. As long as the counting head 49 remains between these two limit positions (i.e., over one of the twenty Y oriented rows of test tubes), the energizing circuit for the light will be complete. If, however, the counting head 49 should be stopped in an X direction beyond either of the outermost Y rows of test tubes, the wiper W1 will leave the conductive segment S1 (at either the interrupted portion 145 or at the opposite end of the segment) and the light 102 will be extinguished, thus generating a home signal. Referring to FIG. 12, it will be noted that the segment S18 is provided with a similar interrupted portion 146 adjacent one end thereof and terminates short of the remaining segments adjacent its opposite end. The arrangement is such that in the event the counting head 49 is indexed to a point beyond either of the outermost X oriented rows of test tubes, the wiper W18 will no longer contact the segment S18 and the light 102 will be extinguished. Thus, the counting head 49 will be automatically homed.

In keeping with the invention, provision is also made for extinguishing the light source 102 (thus homing the counting head 49) whenever samples have been collected in a predetermined number of tubes 48. To accomplish this, it is only necessary to deposit a dummy test tube 148 (FIG. 7) having an upwardly projecting cam surface 149 at the test tube position immediately following the last tube to be filled. A switch actuating and :alined with the vertical bore 101 formed in the counting head 49. The arrangement is such that effluent discharged from the catheter tube 99a (FIG. 7) passes through both the vertical bore 101 and the opening 154 in the cam follower 152, and is collected in the particular test tube 48 positioned thereunder. The switch actuating lever 150 has formed thereon a dimple 155 positioned to pass through an opening 156 formed in the cover 151 so as to engage the actuator MSa of the microswitch M51 when the cam follower 152 engages the cam surface 149 on the dummy test tube 148.

If it is assumed, with reference to FIG. 7, that the counting head 42 is indexing from left to right, then the test tube 48 will have already received its sample of effluent. Effiuent is now discharging into the test tube 48x. When the latter test tube has received its predetermined sample charge, the counting head 49 Will index onestep to the right and the cam follower 152 will engage the cam surface 149 on the dummy test tube 148, thus raising the switch actuating lever 150 and depressing the switch actuator 'MSa. When this occurs the energizing circuit for the light source 192 is opened and the light extinguished, thus generating a home signal for the counting head.

The foregoing arrangement insures that a home signal will be generated for simultaneously energizing both stepping motors SMx and SMy when the counting head 49 is indexed past any of its limit positions, when the light source 102 burns out, or when the light is mechanically turned out by engagement of the cam follower 152 with the cam surface 149 on the dummy test tube 148. When the operator desires to simulta- I neously collect fractions from more than one column. it is only necessary to properly position the dummy test tube 143 so as to insure that the counting head 49 will home after the desired number of fractions have been collected. Of course, it will be understood that the terms home or homing as used herein and in the appended claims are intended to denote an operating cycle in which the counting head 49 is indexed along either or both of the X and Y coordinates so as to return the head to its initial starting position-here the home position over test tube 48h. Merely by way of example, if the operator desires to collect the maximum number of samples from four different columns 41a41d (FIG. 1), the dummy test tube 148 would be positioned in the upper right-hand corner of the rack 28a as viewed in FIG. 2 (i.e., at the test tube position indicated at 480). Therefore, while samples are being successively collected in the first ninety-nine test tubes 43 in the rack 28a, they are simultaneously being collected in the corresponding ninety-nine test tubes for each of the other racks. When the counting head indexes to the tube 48c position, the light 102 will be extinguished and a home signal generated for the stepping motors. Hence, ninety-nine samples are collected in each of the four different racks from each of the four respective columns.

Alternatively, if the operator desires to collect the maximum number of samples from two columns, the dummy test tube 148 would be located in the upper righthand corner of rack 28!; (i.e., at the test tube 48a position). After one hundred ninety-nine fractions have been collected from each of the two sources, the counting head 49 will index to the tube 489 position, extinguishing the light 102, and generating a home signal for the stepping motors.

With the foregoing description in mind, the functions served by the segments S4, S5, S22 and S22 may now be made more explicit. Assume, for example, that the operator desires to collect one hundred thirty-five samples from each of two different sources. With such a requirement, the dummy test tube 148 would be placed at the thirty-sixth test tube position (i.e., position 4311 in FIG. 2) in rack 2317, thus allowing collection of one hundred samples in racks 28a, 28d simultaneously, and collection of thirty-five samples in racks 28b and 28c simultaneously. When the counting head 49 indexes to the next position (i.e., over the tube 48m position) a home signal is generated for both stepping motors SMx and SMy. However, at this particular test tube position, it requires thirteen indexing steps of the Y stepping motor SMy to home the counting head 49 along a Y coordinate and only four indexing steps of the X stepping motor SMx to home the counting head 4% along an X coordinate-that is, to return the counting head 49 to a position overlying test tube 48h.

In order to deenergize the X stepping motor after four indexing steps, the segment S4 (FIG. 9) terminates at a point 158 positioned approximately in the center of the board 134 and in alinement with the home position 4871. As long as the counting head 49 remains to the left of the Y row of tubes 48 including tube 4811 (as viewed in FIGS. 2 and 3), the wiper W4 will contact the segment S4 and the stepping motor SMx will remain energized. The instant that the wiper W4 passes the point 158 and is disengaged from the segment S4, a stop signal is generated for deenergizing the X motor. If the counting head had been positioned over either rack 280 or rack 28d, a similar stop signal would be generated for the X stepping motor when the wiper W passes the terminal portion 159 of segment S5.

In order to deenergize the Y stepping motor after thirteen indexing steps, the closely spaced conductive segments S22, S22 on the inboard face of beam 74 terminate at a point corresponding to home position 48h. When the Wiper W22 contacts both segments S22, S22, a stop signal is generated for the Y stepping motor SMy. This will not occur until the counting head 49 has been indexed rearwardly (downwardly as viewed in FIG. 2) along the cross beam 50 to a position overlying one of the tubes in the X oriented row including test tube 48h.

To insure accurate step-by-step indexing of the counting head 49 along any given X coordinate, provision is made for generating a stop signal for the stepping motor SMx, when the vertical bore 101 in the head 49 is alined with the next tube to be filled. To accomplish this, the segment S17 is provided with a plurality of equally spaced, non-conductive notches 166 (FIG. 9), the spacing between adjacent notches corresponding to the spacing between adjacent test tubes and with the notches being respectively alined with the different Y rows of tubes. Since the non-conductive notches serve as current interrupters, the segment S17 will hereafter be referred to as the X interrupter bus. The X interrupter bus S17 and the segment S16, each of which are coupled to a suitable voltage source (i.e., source 135 shown in FIG. 3), are respectively contacted by wipers W17 and W16. When an indexing or start signal is generated for the motor SMx (e.g., when a predetermined number of drops have been counted into a given tube 48), the carriage 52 starts to translate along the shaft 53 (FIG. 2) in the manner previously described. When this occurs, the wipers W17 leave the non-conductive notches 160 alined with the tube 48 that has just been filled, and engage the conductive portion of the X interrupter bus S17. However, when the carriage 52 translates a distance corresponding to the space between adjacent test tube centers, the wipers W17 contact the next set of notches 160, breaking the circuit including segment S16 and bus S17 and generating a stop signal for the X stepping motor SMx. Such a stop signal is generated each time that the carriage translates to the next tube 48 to be filled.

Referring next to FIG. 11, it will be observed that the segment $23 on the outboard face of beam 74 is also provided with a series of non-conductive, equally spaced notches 161 which here serve to generate stop signals for the Y stepping motor SMy. To this end, the spacing between adjacent notches 161 corresponds tothe spacing between adjacent test tube centers along a Y coordinate, the notches being respectively alined with the X rows of test tubes. When the Y motor is energized to index one step in a Y direction, the wiper W23 associated with the Y interrupter bus S23 leaves the notch 161 alined with the tube 48 that has just been filled and wipes along the bus S23. At the instant it contacts the adjacent notch 161, the circuit including bus 23, wiper 23, segment 24 and wiper 24 is broken, generating a stop signal for the Y motor SMy when the counting head 49 is alined with the next tube to be filled.

With particular reference to FIGS. 14a and 14b, a cycle of operation for the fraction collecting apparatus 25 will now be described in conjunction with the novel control system employed with the present invention. To facilitate an understanding of the invention, the operation will be described in conjunction with a drop counting cycle rather than a time measuring cycle (i.e., the drop counting mode having been selected by the operator by adjustment of the mode selecting switch 164 shown in FIG. 14a).

With the mode selecting switch 164 set for a drop counting operation, the photocell 104 is coupled directly to the input terminal A of a monostable device MMV-1 which may simply take the form of a monostable or one shot, multivibrator. Under normal conditions when no effluent drop 165 is blocking the light source 102, the photocell 104 will conduct heavily, causing a large potential drop across resistor R1 and maintaining a steady potential level (e.g., approximately 10 volts) at the terminal A of the device MMV-l. However, when an effluent drop 165 momentarily blocks the light source 102, the resistance of photocell 194 rises abruptly, decreasing the potential drop across resistor R1 and producing an input signal for the monostable device in the form of a positive-going pulse.

Referring to FIG. 15, there is illustrated a typical monostable device of the type employed in the exemplary control circuit shown in FIGS. 14a and 14b. The input terminal A is here connected through a coupling capacitor C1 to the base 166]; of a normally ON transistor 166. The emitter 166e of transistor 166 is coupled to ground While the collector 166c is coupled to both an output terminal M and, through an RC network 168, to the base 169!) of a normally OFF transistor 169. The transistor 169 has its emitter 169e coupled to ground and its collector 16% coupled to an output terminal N. The arrangement is such that when the monostable multivibrator is in its stable state (i.e., transistor 166 ON and transistor 169 OFF), the output terminal M is at a relatively high potential (approximately 0 volts) and the output terminal N is at a lower potential (approximately 12 volts). When a positive input pulse appears at input terminal A, it will serve to drive the multivibrator to its quasi-stable state (i.e., transistor 166 OFF and transistor 169 ON) for a short period, during which time the potential level at output terminal M will drop sharply and the potential level at output terminal N will abruptly rise (to approximately 0 v.). After the short time period, these latter potentials switch back to their original values.

Referring again to FIG. 14a, it will be observed that the output terminal N (i.e., that terminal normally at a low potential level) is coupled to one input of an AND gate 206, the latter receiving a second input from a bistable device FF-l which may, for example, simply take the form of a transistor flip-flop circuit. Such devices are well known in the art and therefore will not be described in detail here. Suffice it to say that this type of flip-fiop device may have three input terminals A, B and C, and two output terminals M and N. To facilitate the present description, it will be assumed that the terminal A as hereinafter used represent the ON input terminal (i.e., a negative-going pulse applied at A switches the device to the ON state to place output terminal M at a relatively high potential level of 0 volts and output terminal N at a relatively low potential level of 12 volts). Terminal C represents the OFF input terminal (i.e., a pulse applied thereto places terminals M and N at 12 and 0 volts respectively). Input terminal B represents the SWITCH terminal (i.e., that terminal which, in response to an input signal, causes the bi-stable device to change states).

In the exemplary apparatus, the AND gate 170 receives its second input frame terminal M which is held at approximately 12 volts when the bi-stable device FF1 is OFF. To insure that the device FF-l is initially conditioned in its OFF state, its input terminal C is coupled directly to one terminal 171 of a manually controllable reset switch 172. Thus, the AND gate 170 is conditioned to the OPEN state and, upon reception of positive input signal from the monostable device MMV1 (i.e., upon detection of a drop by photocell 104), it will pass a positive output signal which is here routed directly to the input terminal of a conventional counter divider 174 of the type which is selectively adjustable to produce one output pulse for different predetermined numbers of 15 input pulses. As here shown, the counter divider has been set, by adjustment of a selector switch 175, to produce one positive output signal for every ten positive input signals from AND gate 170.

In order to count the number of drops actually deposited into a given test tube 48, the output signal from the counter divider is passed to the input terminal A of a monostable device MMV-Z, the latter having its output terminal M coupled to the coil 176 of an electro-mechanical counter 178 of a type readily available from commercial sources. Such a counter may be manually adjusted by means of a control knob 179 to produce an output signal after a predetermined number of input signals. As shown in the exemplary embodiment of FIG. 14a, the counter 178 is set to count fifty input signals, each of which represents ten drops (because of the setting of the counter divider 174). Hence, each output signal from the counter 178 will here represent 500 drops of effiuent. Each positive input pulse to the counter 178 will reversely step the counter one digit. When the counter counts down to zero," its relay contacts CR1 closed, producing a negative out ut signal which is passed to the OFF terminal C of a flip-flop FI -2', to the input terminal A of a one-shot device MMV-3, and to one input of an AND gate 180,

The one-shot device MMV-3 serves two important functions. First, it provides a positive input signal from terminal N to the coil 176 of counter 178, which signal serves to reset the counter (e.g., from zero back to the original reading of fifty). Secondly, through suitable inverter means, there is provided a negative input signal for terminal C of the bi-stable device FF-l, insuring that the latter remains in its OFF state.

For the purpose of stepping one or the other of the stepping motors SMx, SMy when a negative signal is impressed upon the terminal A of the flip-flop FF2, the output terminal N is coupled to a pair of oppositely conditioned AND gates 181, 132 (i.e., when one gate is open, the other is closed). To condition the gates 181 and 182 in this manner, they respectively receive second input signals from the output terminals M, N of a normally OFF flip-flop FF-3, that is, gate 181 which is coupled to terminal M (12 v.) is open and gate 182 which is coupled to terminal N v.) is closed. The AND gates 181, 182 each receive timed input pulses from a square wave oscillator, which takes the form of a free running multivibrator or blocking oscillator, and is shown diagrammatically in FIG. 14b as a clock 184. Since flip-lop FF-3 is normally OFF and the gate 182 closed, each output signal from the counter 178 will pass only through AND gate 181, the output of that gate being coupled directly to the switch terminal B of a bi-stable device FF4, switching the latter from its previous stable state to its second stable state. The output terminals M, N of flip-flop FF-4 are respectively connected to the switch terminals B of a pair of motor driver flip-flops FF-S, FF-6. Let it be assumed for the purpose of the following description that all three flip-flops FF4, FF5 and FF6 are initially set to the OFF condition.

Under these conditions, the M output terminals of all three flip-flops are at a relatively low potential of -12 v.

, When the gate 181 produces an output signal (i.e., upon closure of the relay contacts CR-1 of the counter 178), flip-flop FF4 will switch to the ON state, thus switching flip-flop FF5 ON. The next input signal to flip-flop FF-4 (the next motor or index signal) will switch it OFF,

thus turning flip-flop FF-6 ON, Successive input signals to flip-flop FF-4 will continue to alternately switch the motor driver flip-flops FF-S, FF-6.

Turning to FIG. 16, an exemplary motor driver flipflop for energizing two of the stepping motor coils has been illustrated. As here shown, there is provided a pair of transistors 185, 186 having their bases 185b, 1861) respectively coupled through RC networks 188, 189 to the collectors 186a, 1850. The emitters 1852, 186e are each SMx continues to run.

coupled directly to ground. The collector 1135c is conected through output terminal M to one coil MC1 of stepping motor SMx, while the collector 1860 is connected through output terminal N to a second coil MC-Z of the motor. Thus, the arrangement insures that switching of the flip-flop from one stable state to the other will alternately energize the coils MC1, MC-Z, the energized coil being that coil coupled to the ON transistor.

As each pulse passes from the clock 134 through the gate 181 to switch the flip-flop FF-4, the coils of the stepping motor SMx are energized in a sequence which causes the motor rotor to angularly step a predetermined amount, and the motor therefore moves the carriage 52 (FIG. '2) a short distance to the left along the X coordinate. Thus, after the first or home test tube has received the requisite number of drops and the counter contacts (ZR-1 have momentarily closed to turn FF-Z ON and open the gate 181, the carriage 52 moves in short steps to the left. As the carriage 52 moves, the wipers W17 will engage electrically a portion of the interrupter bus S17, thereby completing a circuit through a resistor R2, making the potential at the upper end thereof about zero volts. Then, when the head 49 becomes registered with the second tube in the first X row, the wipers W17 will be opposite a notch in the strip S17, and the potential at the upper end of R2 will drop abruptly from zero volts to -12 volts. This negative-going transistor is applied as a pulse to the ON input terminals A of flip-flops FF-7 and FF-3, but the latter are simply left in their ON states. The same negative-going pulse is applied to the A terminal of FF-Z, thus turning the latter ON, and causing the gate 181 to close. This terminates passage of pulses from the clock 184 to FF-4, so that the motor SMx stops with the head 49 accurately located over the second test tube.

The drops passing the photocell 104 are now counted as they fall into the second test tube, and when the counter 178 reaches a zero reading the contacts CR-1 again momentarily close to turn FF-2 ON, open the gate 181 and thus initiate stepping of the motor SMx to move the head 49 to the third tube. The same indexing action repeats until the first nine tubes in the first row have received the predetermined number of drops.

As the ninth tube in the first row of the quadrant rack 28a receives the desired number of drops, the contacts CR-1 will momentarily close to turn FF2 ON, open the gate 181, and thus initiate stepping of the motor SMx to move the head 49 toward the tenth (and last) tube in the row. The contacts CR1 also supply a ninth pulse to the scale-of-nine counter 191), which has received eight previous pulses. Accordingly, the counter supplies an output pulse to the C terminal of FF-7, turning the latter OFF, so that its terminal M switches from a low potential to a high potential. That positive-going voltage transition has no effect on FF-3 or FF-8, and the motor When the head 49 is alined with the tenth tube, however, a negative-going voltage charge is produced across R2, and this serves to turn FF2 ON (thereby stopping the motor), and also to turn FF-7 back ON. The negative-going voltage charge at terminal M of FF-7 is applied to terminal A of FF-3, so that the latter switches to the OFF state, and the voltages at its output terminals M, N thus disable gate 181 and enable gate 182. This means that at the completion of the drop count for the tenth tube, the motor SMy (instead of SMx) will be actuated by clock pulses. Also, the positive-going voltage charge at terminal N of FF-7 is applied to the B terminal of FF-8, switching the state of the latter so that FF4, FF-S and FF-6 are conditioned to make motor SMx run in the opposite direction the next time that pulses pass through the gate 181.

It may be noted here that after the head 49 is registered with the tenth tube in the first row, FF-3 is in the OFF state. The potential of zero volts at its output terminal M is passed as a control signal to the gate 180, so that the latter is closed. This prevents the counter 190 from receiving an input pulse when the counter contacts CR-1 close at completion of drop counting for the tenth tube.

When the drop count for the tenth tube is complete, the contacts CR-l momentarily close to turn FF-2 OFF, and thereby open the gate 182 (gate 181 cannot open because FF-3 in the OFF state has disabled it). Thus, pluses from clock 184 pass through gate 182 to a switching flip-flop FF-9 which controls driver flip-flops FF-10, FF-ll for the motor SMy. Accordingly, the motor SMy begins moving the head toward the second row of tubes (FIG. 2). As the head 49 becomes alined with the eleventh tube, the wiper W23 will register with a notch in the interrupter bar S23, thus producing a negative-going voltage charge across a resistor R3. This is routed to the C terminal of FF-2 so that the latter is turned ON to close gate 182 and stop the motor SMy; this same voltage charge is routed to the C terminals of FF-7 (where it has no effect since the latter is already ON) and of FF-3 (where it switches the latter from OFF to ON). When FF-3 turns ON, the voltages at its output terminals disable gate 182 and enable gate 181, so that the next series of pulses will cause stepping of motor SMx instead of motor SMy.

Next, after the drop count for the eleventh tube is complete, the contacts CR-l momentarily close to turn FF2 OFF, open gate 181, and cause the motor SMx to begin stepping. However, because FF-4, FF5 and FF6 were preset to a different original state by FF-S, the motor SMx now steps in the opposite direction (i.e., from left to right) until it becomes registered with the twelfth tube and a signal from R2 turns FF-2 ON to close the gate 181. Because FF-3 is now again in its ON state, the gate 180 is now enabled, and the pulse produced by momentary closure of contacts CR1 enters the scale-of-nine counter.

From the foregoing it will be apparent that the head is indexed from tube-to-tube, and drops counted in each tube for the first row of the quadrant rack 28a. After the tenth tube has received its liquid drops, the motor SMx is not energized, but rather the motor SMy is energized to move the head 49 in a Y direction (upwardly as viewed in FIG. 2) until it registers with the eleventh tube in the second row. The operation then continues with thehead 49 moving from left to right over successive tubes in the second row. When the last tube in the second row has been filled, the scale of nine counter will have again received nine pulses, so that the motor SMy (instead of SMx) will be energized to move the head 49 over the first tube in the third row. The motor SMx will be conditioned so that it now moves the head from right to left over successive ones of the tubes in the third row, pausing so that the predetermined number of liquid drops are deposited in each tube.

By this arrangement, therefore, the head will progress over and deposit a predetermined number of drops in all the tubes of the racks 28a and 28b, ending with the tube 48e (FIG. 2). When the head 49 moves over the last row in the second quadrant, however, the wiper W22 moves into bridging contact with conductive strips S22a, S2211, thereby completing an energization circuit for a resistor R4 through conductive strips 522a, 822a, S11 and S12, the latter being bridged by wipers W11, W12 so long as the head 49 is in the first or second quadrants. The gate 180 was previously enabled by the 12 volt potential appearing at the resistor R4, but when the strips 822a, 822a are bridged, the potential rises to about zero volts, thereby disabling gate 180 and preventing any input to counter 190. Therefore, after the head has indexed over the last ten tubes in the second quadrant, it continues to index from left to right over the first row (uppermost, FIG. 2) in the third quadrant. However, as the head moves along the X direction from the tube 48:: into the third quadrant, the wiper W11 moves free of strip S11, thereby braking the circuit for R4 and producing a negative-going voltage charge at the latter. This does two things. First, it supplies a negative potential to terminal a of gate 180, so the latter is now enabled and the scale-of-nine counter receives pulses. That counter will therefore control FF-7 and FF-3 as previously described so that after the head has been registered with the tube in the upper right corner (FIG. 2), the motor SMy will receive clock pulses instead of motor SMx. Secondly, that negative-going voltage charge at R4 is routed to the A input terminal of FF-9 to preset the latter to the ON state, and thus to reverse the direction of rotation of motor SMy (i.e., to make it drive the head downwardly as viewed in FIG. 2). The operation previously described now continues with the head 49 being moved successively over the test tubes in the third and fourth quadrant racks until it reaches the home position.

As previously noted, the present apparatus and control system serves to cause the head 49 automatically to move back to its home position when certain events transpire. For this purpose, the lamp 102 on the head 49 is energized normally by current flow through a series circuit extending between positive and negative terminals of a suitable voltage source. As shown in FIG. 14a, the series circuit extends from the positive source terminal through conductive strip S6, wiper W6, strip S19, wiper W19, normally closed switch MSl, lamp 102, wiper W18, strip S18, wiper W1, strip S1, and a resistor R5 to the negative terminal of the voltage source. Normally, therefore, the lamp 102 is energized, and the apparatus functions in the manner described above, the potential at the upper end of R5 being approximately 3 volts due to the voltage drop across the lamp filament and the resistor R5.

Any of several conditions can interrupt the series circuit shown in FIG. 14. These are: (l) the lamp 102 burns out and its filament breaks, (2) the switch arm 150 strikes a dummy tube 149 to open the normally closed switch MSl, (3) the head attempts to overtravel in either direction along the Y axis so that the wiper W18 moves free of the conductive strip S18, or (4) the carriage 52 attempts to overtravel in either direction along the X axis so that the wiper W1 moves free of the conductive strip 51. In any of these events, the voltage appearing at the upper end of resistor R5 will switch from about 3 volts to about -12 volts. This negative voltage here termed the home signal, appears on a conductor leading to a control terminal 196a of a gate 196 (FIG. 14b).

The gate 196 is normally closed but is opened by the home signal so that it passes pulses generated by an associated pulse oscillator or clock 197. The output from the opened gate 196 leads to input terminals of two associated gates 200, 201 which are opened or closed according to the potentials appearing on their control terminals 209a and 201a.

The terminal 200a is connected to the upper end of a resistor R6 which is connected to both the conductive strips S4 and S5, the latter being spaced apart to leave a gap occupied by a wiper W4 when the head 49 is-in the X home position. Thus, wipers W4 and W5 will provide a current flow path through R6 except when the head 49 is at X home; and the voltage applied to terminal 200a through an inverter 202 will thus open the gate 200 except when the head is at X home position.

Similarly, the terminal 291:: is connected to a resistor R7 which is connected in a series which includes conductive strips S22, S22. The latter strips are bridged by a wiper W22 to make the control voltage about zero volts (and thus to close gate 201) only when the head 49 is in a 4 home position, i.e., when the head is over the lowermost row of tubes as shown in FIG. 2.

With this in mind, it will be seen that in response to a home signal on conductor 195, pulses will be passed from clock 197 through gate 196; and thence through gates 2110 and 201 to the C terminals of FF-4 and FF9. This will cause pulsing of both the motors SMx and SMy to move the carriage 52 and the head 49. As soon as the carriage 52 is centered at the X home position, the voltage at resistor R6 causes the gate 200 to close, so that Iii the motor SMx stops. As soon as the head 49 is returned to the Y home position, the wiper W22 bridges strips S22, S22 and the voltage at resistor R7 closes gate 201 to stop the motor SMy. Thus, if malfunctioning (burnout of lamp 102, or overtravel in the X or Y directions) should occur, the head is automatically sent back to its home position. And the same response occurswhen the dummy tube 149, placed at a location in the racks, is engaged to open the switch M81. By this arrangement, the same components are employed to guard against malfunctioning and to make possible collection of samples which in number are less than the total capacity of the four quadrant racks.

In liquid chromatography, it is often the case that many successive samples will contain little or no substances of interest, since these wash through the column at spaced time intervals. To locate those samples which are of interest for further detailed analysis, it is often desired to screen aliquot samples by relatively simple means such as a colorimeter, and to give more detailed analysis to the corresponding main samples where the colorimeter indicates a substance to be present.

To cause a small aliquot sample to be collected in every other test tube, and a larger main sample to be collected in alternate test tubes, the selector knob 205 is moved to the aliquot position (FIG. 14a) to correspondingly set the switch 172. The operation then proceeds as described below.

When the drops pass through the head 49 into the first test tube, the flip-flop FF-l is in its OFF state so that the gate 206 is closed and the gate 170 is open. Pulses formed by each drop thus pass into the counter divider 174. If the latter is set to a ratio of ten, and the counter present to fifty, a totalof five-hundred drops will be collected in the first tube, as previously described.

When that count is complete, the contacts CR-1 momentarily close and will thus produce a pulse on the A terminal of MMV-3 and the latter will produce an output pulse which is routed through a diode to the coil 176, thereby resetting the counter 178. This same output pulse from MMV-3 also passes through an inverter 207 and the switch 172 (which is in the position opposite to that shown in FIG. 14a) to the B or switch input terminal of FF-1. Accordingly, the flip-flop FF-ll is turned on, so that the potentials at its output terminals M, N now open the gate 206 and close the gate 170. The head 49 is now registered with the second test tube, but drop-count pulses created by the photocell 104 and tht MMV-l now pass through the gate 206 directly to MMV2 and thence to the coil 176. This means that the counter 17% will return to zero and momentarily close the contacts CR-1 after only fifty drops enter the second test tube. The head 49 then indexes to the third tube, but closure of the contacts CR4 not only results in MMV-3 sending a reset pulse to the counter coil 176, but also in another pulse being applied to the B input terminal of FF1. This turns the latter OFF, closes the gate 206 and opens the gate 170. Thus, five hundred drops will be passed into the third test tube. In this way, every other tube will receive '500 drops, and alternate tubes will receive aliquot samples of 50 drops.

By changing the ratio of the counter divider 174 through appropriate setting of the dial 175, the relative sizes of the main samples and aliquot samples may be varied.

The present apparatus will be useful also in measuring 01f different time periods during which drops are passed into each sample tube, rather than to count the number of drops. This will be the preferred mode of operation when samples from two or more columns or sources are being simultaneously collected. To do this, the selector switch 164 is set to the time position (FIG. 14a), so that the pulses produced across resistor R1 and fed to the onesho device MMV-l originate in the photocell 130 rather than the photocell 104. Since the motor 125 rotates at constant speed and the chopper 128 darkens the photocell 130 at regularly timed intervals, a predetermined time period of liquid collection in each tube will elapse before the counter 178 is returned to zero. The time interval may, of course, be charged by changing the original setting of the counter divider and the counter 178, Aside from this difference, however, the apparatus functions in the same manner during operation in the time mode as has been previously described for the count" mode. It is significant to observe that substantially all of the control components in FIGS. 14a and 14b are used in both modes, and very little additional hardware is necessary to make possible optional operation in either mode.

When it is desired to collect samples simultaneously from two or more columns, the arms will be coupled to the head to receive the additional catheter tubes, as previously described. Preferably, the apparatus will be operated in the time mode. To terminate the collecting cycle after ninety-nine samples have been collected from each of two chromatographic columns, a dummy tube will be located at the last position in the second quadrant rack. When the head 49 reaches that position, the switch M81 will beopened, and the head will be returned to its home position as previously described. On the other hand, if samples are being collected from four columns into tubes held by the four quadrant racks, the dummy tube will be placed in the last position of the first quadrant, and the head will be returned home after the four catheter tubes have been indexed successively over the sample tubes held in the four respective quadrant racks.

We claim as our invention:

1. In a fraction collecting apparatus of the type having a stationary frame with a quadrated rectangular array of sample containers mounted therein, said containers equally spaced in rows along X and Y coordinates of said array, a head carried by said frame and movable with respect thereto along said X and Y coordinates to posit-ions overlying diiferent ones of said containers, said head adapted to discharge liquid fractions into the underlying container; a rectilinear indexing mechanism comprising, in combination, means for indexing said head from a start position in a given quadrant along a first X oriented row of said containers to successively position said head over each container in said row, means for indexing said head to the next adjacent X oriented row of containers, means for indexing said head along said last'named row in a direction opposite to the indexing movement in said first row, means for repetitively alternating the direction of indexing movement of said head along adjacent X oriented rows until each row in said given quadrant is traversed by said head, and means for repeating said alternatrng indexing movements sequentially through each quadrant of said sample containers.

2. In a fraction collecting apparatus of the type having a stationary frame with a rectangular array of sample containers mounted therein, said containers equally spaced in rows along X and Y coordinates of said array, a head carried by said frame and movable with respect thereto along said X and Y coordinates to positions overlying different ones of said containers, said head adapted to discharge liquid fractions into the underlying container; a rectilinear indexing mechanism comprising, in combinatron, means for indexingsaid head from a start position In said array along a first X oriented row of said contarners to successively position said head over each contamer in said row, means for indexing said head to the next adjacent X oriented row of containers, means for indexing said head along said last named row in a directron opposite to the indexing movement in said first row, and means for repetitively alternating the direction of rndexrng movement of said head along adjacent X oriented lrlowg until each row in said array is traversed by said 3. A liquid fraction collector comprising, in combinatron, a frame, a rectangular quadrated array of sample containers mounted within said frame, said containers disposed in rows long X and Y coordinates within each quadrant of said array and with each X oriented row having it containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in a quadrant, second reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means for successively energizing said first power means n-l times to index said head to positions overlying each container in a given X oriented row, means for energizing said second power means one time upon completion of a filling cycle for the last container in said given X oriented row, means for reversing said first power means, means for successively energizing said first power means n-l times to cause translation of said head in a reverse direction, means for alternately energizing said second power means one time and said first power means n1 times to cause incremental translation of said head over each container in said quadrant, and means for sequentially indexing said head through each quadrant of said array.

4. A liquid fraction collector comprising, in combination, a frame, a rectangular quadrated array of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within each quadrant of said array and with each X oriented row having n containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates, a plurality of extension arms carried by said head and terminating over corresponding containers in different quadrants, means for conducting liquid fractions from a plurality of sources to respective ones of said extension arms for discharge into the underlying containers, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in a quadrant, second reversible power means fo incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means for successively energizing said first power means n1 times to index said head to positions overlying each container in a given X oriented row, means for energizing said second power means one time upon completion of a filling cycle for the last container in said given X oriented row, means for reversing said first power means, means for successively energizing said first power means nl times to cause translation of said head in a reverse direction, means for alternately energizing said second power means one time and said first power means n-l times to cause incremental translation of said head over each container in said quadrant, and means for homing said head upon complete translation over less than all quadrants of said array.

5. A liquid fraction collector comprising, in combination, a frame, a rectangular quadrated array of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within each quadrant of said array and with each X oriented row having n containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates, said head adapted to be coupled to a liquid source for passing drops of liquid into said containers, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in a quadrant, second reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means producing first output signals responsive to the number of drops of liquid passed into each of said containers, means producing timed second output signals, means for selectively counting said first and second output signals, said counting means adapted to generate an index signal for energizing said first and second power means upon counting a selectable number of output signals from the selected one of the means producing said first and second output signals, first means for gating said first power means on nl times in response to 11-1 index signals, second means for gating said second power means on in response to a single index signal, said first and second gating means being complementary, means conditioning said first power means for reverse cycling each time said second power means is gated on, means for sequentially indexing said head through each quadrant of said array, and means for conditioning said second power means for reverse cycling when said counting head has traversed all of the X oriented rows in the first two quadrants.

6. A liquid fraction collector comprising, in combination, a frame, a rectangular quadrated array of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within each quadrant of said array and with each X oriented row having 11 containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates, said head adapted to be coupled to a liquid source for passing drops of liquid into said container, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in a quadrant, second reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means producing output signals responsive to the number of drops of liquid passed into said container, means for counting said output signals, said counting means adapted to count all output pulses representative of drops in alternate containers and a multiple of said output pulses representative of drops in intervening containers, said counting means adapted to generate an index signal for energizing said first and second power means upon counting a selectable number of output signals, first means for gating said first power means on n'1 times in response to 12-1 index signals, second means for gating said second power means on in response to a single index signal, said first and second gating means being complementary, and means conditioning said first power means for reverse cycling each time said second power means is gated on.

7. In a fraction collecting apparatus of the type having a stationary frame with a plurality of rectangular arrays of sample containers mounted therein, said arrays disposed in side-Pby-side relation, said containers equally spaced in rows along X and Y coordinates of each of said arrays, a head carried by said frame and movable with respect thereto along said X and Y coordinates to positions overlying different ones of said containers, said head adapted to discharge liquid fractions into the underlying container; a rectilinear indexing mechanism comprising, in combination, means for indexing said head from a start position in a given array along a first X oriented row of said containers to successively position said head over each container in said row, means for indexing said head to the next adjacent X oriented row of containers in said given array, means for indexing said head along said last named row in said given array in a direction opposite to the indexing movement in said first row, means for repeti-- tively alternating the direction of indexing movement of said head along adjacent X oriented rows until each row in said given array is traversed by said head, and means for repeating said alternating indexing movements sequentially through each adjacent array of said sample containers.

8. In a fraction collecting apparatus of the type having a stationary frame with a rectangular array of sample containers mounted therein, said containers equally spaced in rows along X and Y coordinates of said array, a head carried by said frame and movable with respect thereto along said X and Y coordinates to positions overlying different ones of said containers, said head adapted to discharge liquid fractions into the underlying container; a rectilinear indexing mechanism comprising, in combination, means for indexing said head from a start position in said array along a first X oriented row of said con tainers to successively position said head over each container in said row, means for indexing said head to the next adjacent X oriented row of containers, means for indexing said head along said last named row in a direction opposite to the indexing movement in said first row, means for repetitively alternating the direction of indexing movement of said head along adjacent X oriented rows until each row in said array is traversed by said head, and means for selectively and automatically returning said head to said start position from aposition overlying any selectable one of the sample containers disposed in said array. I

9.- A liquid fraction collector comprising, in combination, a stationary frame, a rectangular array of sample containers mounted on said frame, said containers equally spaced in rows along X and Y coordinates of said array, a head carried by said frame and movable with respect theretoalong said X and Y coordinates to positions overlying different ones of said containers, said head adapted to be coupled to a liquid source for discharging liquid fractions into the underlying container, and a rectilinear indexing mechanism for said head, said indexing mechanism including means for indexing said head from a start position in said array along a first X oriented row of said containers to successively position said head over each container in said row, means for indexing said head to the next adjacent X oriented row of containers, means for indexing said head along said last named row in a direction opposite to the indexing movement in said first row, and means for repetitively alternating the direction of indexing movement of said head along adjacent X oriented rows until each row in said array is traversed by said head.

10. A liquid fraction collector comprising, in combination, a frame, a rectangular array of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within said array and with each X oriented row having it containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates, said head adapted to be coupled to a liquid source for passing drops of liquid into said containers, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in said array, second reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means producing output signals responsive to the number of drops of liquid passed into each of said containers, means for counting said output signals, said counting means adapted to generate an index signal for energizing said first and second power means upon counting a selectable number of output signals, first means for gating said first power means on n1 times in response to 11-1 index signals, second means for gating said second power means on in response to a single index signal, said first and second gating means being complementary, and means conditioning said first power means for reverse cycling each time said second power means is gated on.

11. A liquid fraction collector comprising, in combination, a frame, a rectangular array of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within said array and with each X oriented row having it containers, a head. carried by said frame and indexable with respect thereto along'said X and Y coordinates, said head adapted to be coupled to a liquid source for passing drops of liquid into said containers, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in a quadrant, second. reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, meansproducing timed output signals, means for counting said output signals, said counting means adapted to generate: an index signal for energizing said first and second power: means upon counting a selectable number of output sig-- nals, first means for gating said first power means on a n1 times in response to 11-1 index signals, second means for gating said second power means on in response to a single index signal, said first and second gating means being complementary, and means conditioning said first power means for reverse cycling each time said second power means is gated on.

12. A liquid fraction collector comprising, in combination, a frame, a pair of side-by-side rectangular arrays of sample containers mounted within said frame, said containers disposed in rows along X and Y coordinates within each of said arrays and with each X oriented row having 11' containers, a head carried by said frame and indexable with respect thereto along said X and Y coordinates to positions overlying each container in a given one of said arrays, an extension arm carried by said head and terminating over a corresponding container in the other of said arrays, means for conducting liquid fractions from diiferent sources to respective ones of said head and said extension arm for discharge into the underlying containers, first reversible power means for incrementally stepping said head in opposite directions along adjacent X oriented rows in said given array, second reversible power means for incrementally stepping said head along a Y coordinate a distance corresponding to the spacing between adjacent X oriented rows, means for successively energizing said first power means n-l times to index said head to positions overlying each container in a given X oriented row, means for energizing said second power means one time upon completion of a filling,

cycle for the last container in said given X oriented row, means for reversing said first power means, means for successively energizing said first power means n1 times to cause translation of said head in a reverse direction, and means for alternately energizing said second power means one time and said first power mean n-1 times to cause incremental translation of said head over each container in said given array so that liquid fractions are simultaneously collected in corresponding sample containers in each of said arrays.

References Cited by the Examiner UNITED STATES PATENTS 2,493,382 1/50 3611 141130 2,604,248 7/52 Gorham l41-130 2,709,974 6/55 Hunter et al. 1077 2,880,764 4/59 PelaV-in 141130 2,956,382 10/60 Wardell 5335 3,040,381 6/62 Pioch 141232 XR LAVERNE D, GEIGER, Primaly Examiner. 

1. IN A FRACTION COLLECTING APPARATUS OF THE TYPE HAVING A STATIONARY FRAME WITH A QUADRATED RECTANGULAR ARRAY A SAMPLE CONTAINERS MOUNTED THEREIN, SAID CONTAINERS EQUALLY SPACED IN ROWS ALONG X AND Y COORDINATES OF SAID ARRAY, A HEAD CARRIED BY SAID FRAME AND MOVABLE WITH RESPECT THERETO ALONG SAID X AND Y COORDINATES TO POSITION OVERLYING DIFFERENT ONES OF SAID CONTAINERS, SAID HEAD ADAPTED TO DISCHARGE LIQUID FRACTIONS INTO THE UNDERLYING CONTAINER; A RECTILINEAR INDEXING MECHANISM COMPRISING, IN COMBINATION, MEANS FOR INDEXING SAID HEAD FROM A START POSITION IN A GIVEN QUADRANT ALONG A FIRST X ORIENTED ROW OF SAID CONTAINERS TO SUCCESSIVELY POSITION SAID HEAD OVER 